linux-kernel - Re: nouveau. swiotlb: coherent allocation failed for device 0000:01:00.0 size=2097152

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Message-ID: <e1b8dd62-4423-2b51-9634-e8938801b5d9@gmail.com>
Date:   Tue, 19 Dec 2017 14:45:05 +0100
From:   Christian König <ckoenig.leichtzumerken@...il.com>
To:     Michel Dänzer <michel@...nzer.net>,
        Tobias Klausmann <tobias.johannes.klausmann@....thm.de>,
        Mike Galbraith <efault@....de>
Cc:     nouveau <nouveau@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Ben Skeggs <bskeggs@...hat.com>
Subject: Re: nouveau. swiotlb: coherent allocation failed for device
 0000:01:00.0 size=2097152

Am 19.12.2017 um 11:39 schrieb Michel Dänzer:
> On 2017-12-19 11:37 AM, Michel Dänzer wrote:
>> On 2017-12-18 08:01 PM, Tobias Klausmann wrote:
>>> On 12/18/17 7:06 PM, Mike Galbraith wrote:
>>>> Greetings,
>>>>
>>>> Kernel bound workloads seem to trigger the below for whatever reason.
>>>>    I only see this when beating up NFS.  There was a kworker wakeup
>>>> latency issue, but with a bandaid applied to fix that up, I can still
>>>> trigger this.
>>>
>>> Hi,
>>>
>>> i have seen this one as well with my system, but i could not find an
>>> easy way to trigger it for bisecting purpose. If you can trigger it
>>> conveniently, a bisect would be nice!
>> I'm seeing this (with the amdgpu and radeon drivers) when restic takes a
>> backup, creating memory pressure. I happen to have just finished
>> bisecting, the result is:
>>
>> 648bc3574716400acc06f99915815f80d9563783 is the first bad commit
>> commit 648bc3574716400acc06f99915815f80d9563783
>> Author: Christian König <christian.koenig@....com>
>> Date:   Thu Jul 6 09:59:43 2017 +0200
>>
>>      drm/ttm: add transparent huge page support for DMA allocations v2
>>
>>      Try to allocate huge pages when it makes sense.
>>
>>      v2: fix comment and use ifdef
>>
>>
> BTW, I haven't noticed any bad effects other than the dmesg splats, so
> maybe it's just noise about transient failures for which there is a
> proper fallback in place.

Yeah, I think that is exactly what happens here.

We try to allocate a huge page, but fail and so fall back to using 
multiple 4k pages instead.

Going to send out a patch to suppress the warning.

Thanks for bisecting this,
Christian.